Batboard

I have this question that I wasn't able to crack. Motorola GM360 mounted in the cab of a fire engine. Through the front panel the DTMF mike is connected. We would like to connect a secondary mike in the back of the truck for the pump operator. Speaker is easy, pins 1&7 at the accessory connector.

How about the original microphone (non DTMF) to connect through the accessory connector. I can setup PTT (with codeplug update ofc) to be on pin 3 (to ground pin 7) but:

1) the original mike has quite a bit of circuitry for keying and needs to get power from the radio (potentially pin 13?) and how to actually get this connected?
2) the original installation manual has visor mounted mic between ground and pin 2

In any case, anybody did this successfully? It's pretty common on fire engines from where I am, but I don't have readily available access to the people who did it (like the fire engine outfitters, which is way beyond the volunteer fire budget). So is there a way to do this with gm360, or should we rather think about a new radio?

Suffice is to say that we would like to connect the original motorola rugged mic, not any kind of aftermarket deal, it's a fire engine, so certain reliability is a must:)

I wasn't really lucky searching the forum, besides quite a few people asking the same question, not really a straight answer in a wiring diagram.

To be honest from the questions you're asking I think a second radio install is the safest option. A second hand '360 will be cheaper than outfitter labour rates.

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First thing, DO NOT CONNECT THE SPEAKER TO PIN 7!!!!!!!!!! You will FRY the audio amp IC.
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The speaker audio is on pins 1 and 16, opposite corners of the connector.

You should be able to hook up an external mic to the accessory connector, haven't had to do one in a while but I'll look into it when I'm at the shop tomorrow and post what info I have.

Okay, found some of what I was looking for..

You basically need on the accessory connector is Mic Audio (pin 2) PTT (pin 3) and Ground (pin 7). I believe you can also do Hang Up with one of the programmable I/O pins, but I'll have to look into that further.
What we usually do is run a cable from the accessory connector to an 8 pin modular jack and plug the mic into that. I'll look to see if I've got the exact wiring for the mic jack.
You don't need power for the mic, it gets it's operating voltage from the Mic Audio line.

I would really appreciate the wiring diagram. Never figured the accesory mic pic is also powered, which would explain a lot. One thing is certain, that powering the mic theough decoupling cap didn’t work.

And i have the speaker connected correctly as you indicate.

SO I'm taking the mic wirign diagram from here: http://www.zendamateur.com/viewtopic.php?f=4&t=8806

and using that connecting directly to the gm360 accessory connector (by the way, I have the speaker connected correctly as you have indicated, just checked that, the original post was written from memory).

Wish me luck, I'll reffer later if that works. I have created a short pigtail with keystone jack to just test it in the cab, then I'll wire the thing finally to the back of the engine.

ON a side note, if you want to save a dolar on the motorola accessory plug (which is in my part of the world for about equivalent of 10 american dollhairs) you can use 2x10 dupont connectors instead, for much better price. It doesn't have the fancy cable relief like the original has, but that is found to be a non issue in our application...

Just make sure you get the microphone plug wiring the right way around, Motorola always numbered their modular connector pins backwards which confuses a lot of people.
If you want hang-up functionality you have to program one of the I/O pins for it, pins 6, 8, 12 and 14 should all have the Mic Off Hook option.

Do you have an idea if the wiring diagram linked above is correct? At least the colors? I could easily confirm ground and of hook, but not the rest.

Also I fon’t have immediate use for the off hook feature, what is that normally used for?

So the short version is, it works!

For future generations, I've used the wiring digram that I've linked above as the mic side which translates as:
Red (mic Audio): Pin 2
Green (PTT): Pin 3
Black (GND): Pin 7

suffice it to say, that the mic has a 10ping RJ45 plug, and so the RJ 45 socket has to start using pin 2, which is Orange, the green-white, then blue in the ethernet cable. I don't have the hodge podge pigtail that I made to test this with me right now, but the colors from the wiring diagram match. If I get around to it, I'll post the color matching documentation.

In any case, thank you very much for pointing me in the right direction!

taboracek wrote: Also I don’t have immediate use for the off hook feature, what is that normally used for?

That is normally used to disable scan and/or put the radio in monitor mode (disable PL) when the user takes the mic off the clip.

So for future generations I'd like to document the complete thing:

So if on one end a standard UTP socket is used, punched using T568B standard, then the motorola accessory connector should be wired as follows:
Green-white -> pin3 (PTT)
Blue -> pin2 (mic Audio)
Blue-White -> pin 7 (GND)

Then (at least) the motorola MDRMN4025D microphone can be just plugged into the socket and works as additional mic to the radio. Didn't tested what happens if both PTTs are activated tough:)

I've also used the brown pair to route the speaker from pins 1 and 16.

Now we basically have a second set of radio "talking" controls at the back of the fire engine for the pump operator to speak to dispatch or the tactical channel. I'm thinking about a button to toggle between the tac and dispatch channels connected on pins 6 or 8 if the CPS allows for that.